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The researchers were able to identify the minimal conditions and factors that would be sufficient for starting the cascade of molecular and cellular processes to instruct pluripotent cells to organize the embryo. (wikipedia.org)
They showed that opposing gradients of bone morphogenetic protein (BMP) and Nodal, two transforming growth factor family members that act as morphogens, are sufficient to induce molecular and cellular mechanisms required to organize, in vivo or in vitro, uncommitted cells of the zebrafish blastula animal pole into a well-developed embryo. (wikipedia.org)
2. Nuclear transfer is a technique used to duplicate genetic material by creating an embryo through the transfer and fusion of a diploid cell in an enucleated female oocyte.2 Cloning has a broader meaning than nuclear transfer as it also involves gene replication and natural or induced embryo splitting (see Annex 1). (who.int)
But it is perhaps not auspicious to quote him for purposes of the scientific debates on human cloning, because Ramsey agreed with and supported the scientific myth of the "pre-embryo" 47 made famous by Jesuit Richard McCormick and frog embryologist Clifford Grobstein. (lifeissues.net)
In animals , parthenogenesis means development of an embryo from an unfertilized egg cell. (alchetron.com)
Gynogenesis and pseudogamy are closely related phenomena in which a sperm or pollen triggers the development of the egg cell into an embryo but makes no genetic contribution to the embryo. (alchetron.com)
He and his team described the biological processes related to reproductive cyclicity, sperm, egg and embryo development in carnivores, especially felids and canids. (si.edu)
This question had been asked by embryologists since 1886 ( Rauber, 1886 ), and Spemann ( Spemann, 1938 ) had demonstrated by an egg ligation experiment that the nuclei of an eight-cell frog embryo are developmentally totipotent. (biologists.com)
However, Briggs and King ( Briggs and King, 1957 ) had also found that the nucleus of an endoderm cell from a neurula embryo could no longer support normal development ( Fig. 2 ). (biologists.com)
Fourth, each cell of the developing frog embryo contains yolk platelets that provide nutrition during prefeeding stages of embryonic life. (biomedcentral.com)
An organizer population has been identified in the anterior end of the primitive streak of the mid-streak stage embryo, by the expression of Hnf3β , Gsc lacZ and Chrd , and the ability of these cells to induce a second neural axis in the host embryo. (silverchair.com)
This cell population can therefore be regarded as the mid-gastrula organizer and, together with the early-gastrula organizer and the node, constitute the organizer of the mouse embryo at successive stages of development. (silverchair.com)
Fine mapping of the epiblast in the posterior region of the early-streak stage embryo reveals that although the early-gastrula organizer contains cells that give rise to the axial mesoderm, the bulk of the progenitors of the head process and the notochord are localized outside the early gastrula organizer. (silverchair.com)
Cells that are fated for the head process move anteriorly from the mid-gastrula organizer in a tight column along the midline of the embryo. (silverchair.com)

The process involves sucking out the nucleus of a somatic (body) cell and injecting it into an oocyte that has had its nucleus removed Using an approach based on the protocol outlined by Tachibana et al. (wikipedia.org)
In the 1960s, the early days of stem cell research, John Gurdon was a student in the U.K. when he began working on cloning - transplanting the nucleus from the cell of one organism into the egg of another where the nucleus had been removed. (regenhealthsolutions.info)
The nucleus of an adult somatic cell (such as a skin cell) is removed and transferred to an enucleated egg, which is then stimulated with electric current or chemicals to activate cell division. (who.int)
However, an animal created through this technique would not be a precise genetic copy of the source of its nuclear DNA because each clone derives a small amount of its DNA from the mitochondria of the egg (which lie outside the nucleus) rather than from the donor of cell nucleus. (who.int)
Thus, the clone would be genetically identical to the nucleus donor only if the egg came from the same donor or from her maternal line. (who.int)
It was clear that a definitive experiment required the replacement of a zygote nucleus by a somatic cell nucleus, asking whether the somatic nucleus could functionally replace the zygote nucleus by eliciting normal development of the enucleated recipient egg ( Fig. 1 )? (biologists.com)
Briggs and King ( Briggs and King, 1952 ) had already succeeded in transplanting a blastula cell nucleus into an enucleated egg and obtaining normal tadpoles in the frog Rana pipiens . (biologists.com)
A) Unfertilized egg and diploid blastula 24 h, (B) haploid androgenetic blastula 24h, (C) axolotl activated egg implanted with Pleurodeles blastula nucleus, diploid, (D) axolotl activated egg, implanted with Pleurodeles haploid androgenetic nucleus, (E) same experiment as D, except a transient treatment with spermine of the transplanted nucleus. (silverchair.com)

iPS cells could potentially be used to generate cell types that could be transplanted to replace those lost or damaged in organs or tissues due to injury or disease. (regenhealthsolutions.info)
We propose that quantitative experimental embryology offers essential ways to explore the reaction of cells and tissues to targeted cell addition, removal, and confinement. (mdpi.com)
For instance, effective transfer of programmable nucleases to living cells, tissues, or organs that contain the target gene is important for genome editing. (molcells.org)
This allows explanted cells to survive in simple salt solutions for several days and enables study of isolated embryonic tissues and cells. (biomedcentral.com)
It cannot be detected in the unfertilized egg, sperm or differentiated tissues such as liver or muscle. (silverchair.com)

Induced totipotent cells can be obtained by reprogramming somatic cells with somatic-cell nuclear transfer (SCNT). (wikipedia.org)
Somatic-cell nuclear transfer, the technique by which Dolly was created, was first used 40 years ago in research with tadpoles and frogs. (who.int)
if it implants and the pregnancy goes to term, the resulting individual will carry the same nuclear genetic material as the donor of the adult somatic cell. (who.int)
Scientists were initially interested in somatic-cell nuclear transfer as a means of determining whether genes remain functional even after most of them have been switched off as the cells in a developing organism assume their specialized functions as blood cells, muscle cells, and so forth. (who.int)
As a brand new graduate student starting in October 1956, my supervisor Michail Fischberg, a lecturer in the department of Zoology at Oxford, suggested that I should try to make somatic cell nuclear transplantation work in the South African frog Xenopus laevis . (biologists.com)

Some types of mature, specialized adult cells can naturally revert to stem cells. (wikipedia.org)
While they normally produce digestive fluids for the stomach, they can revert into stem cells to make temporary repairs to stomach injuries, such as a cut or damage from infection. (wikipedia.org)
Differentiated airway epithelial cells can revert into stable and functional stem cells in vivo. (wikipedia.org)
His experiments demonstrated that a mature cell, one that was fully differentiated, could revert to an earlier state when introduced into a developing egg, in this case a frog tadpole. (regenhealthsolutions.info)
In fact, in the right environment, adult cells could revert to an earlier, embryonic cell type that would be capable of giving rise to all the specialized cell types present in an adult organism. (regenhealthsolutions.info)
The fact that the DNA of a fully differentiated (adult) cell could be stimulated to revert to a condition comparable to that of a newly fertilized egg and to repeat the process of embryonic development demonstrates that all the genes in differentiated cells retain their functional capacity, although only a few are active. (who.int)

The frog Xenopus laevis has been used to study early stages of vertebrate development for more than 50 years and continues to be an important model system. (biomedcentral.com)
In the axolotl, DNA-ligase I (8S) is specific for embryonic stages. (silverchair.com)

During the life cycle of flowering plants, nuclear fusion occurs three times: once during female gametogenesis and twice during double fertilization, when two sperm cells fertilize the egg and the central cell. (preprints.org)

hESCs can be generated by SCNT using dermal fibroblasts nuclei from both a middle-aged 35-year-old male and an elderly, 75-year-old male, suggesting that age-associated changes are not necessarily an impediment to SCNT-based nuclear reprogramming of human cells. (wikipedia.org)
Even advanced donor cells from the endoderm of Xenopus tadpoles have nuclei that can sometimes yield normal individuals after nuclear transfer [data taken from Briggs and King ( Briggs and King, 1957 ) for Rana and from Gurdon ( Gurdon, 1962 ) for Xenopus ]. (biologists.com)

Normal egg cells form after meiosis and are haploid, with half as many chromosomes as their mother's body cells. (alchetron.com)

Transposable elements will provide invaluable tools for manipulating the frog genome. (biomedcentral.com)
The high fecundity of the frog combined with the ability to remobilize transposon transgenes integrated into frog genome will allow large-scale insertional mutagenesis screens to be performed in laboratories with modest husbandry capacities. (biomedcentral.com)
The closely related frog Xenopus tropicalis shares all the features of X. laevis that make this system useful for embryonic manipulation but it develops more rapidly (sexual maturity is reached in 5 to 9 months) and has a diploid genome. (biomedcentral.com)
Here, we review the application of transposable elements to modification of the frog genome. (biomedcentral.com)
Once integrated into the frog genome, the 'cut-and-paste' DNA transposons are targets for remobilization by re-expression of the appropriate transposase enzyme. (biomedcentral.com)
Let's transplant the genome of species A in a cell of species B and see whether the resulting individuals will resemble species A, species B, or something else. (blogspot.com)
If you are correct, then the result should not look like the genome donor species A, right? (blogspot.com)

Induced stem cells (iSC) are stem cells derived from somatic, reproductive, pluripotent or other cell types by deliberate epigenetic reprogramming. (wikipedia.org)
5. In 2001, France and Germany requested the United Nations General Assembly to develop international conventions on human reproductive cloning, therapeutic cloning and research on stem cells. (who.int)
With stem cell biology and molecular understanding of reproductive failure, new therapies for previously untreatable infertility are currently on the near horizon. (infertile.com)

Fruit flies of the species Drosophila melanogaster develop from eggs to adults in eight to ten days at 25 degrees Celsius. (asu.edu)
David Wildt leads the Center for Species Survival team that has generated much of what we now know about how many wildlife species reproduce (from frogs to elephants). (si.edu)
Third, many amphibian species lay vast numbers of eggs, providing adequate numbers for study. (biomedcentral.com)

The frog Xenopus laevis has been an important model of vertebrate cell biology and development for many decades. (biomedcentral.com)

Mature egg cells are produced by mitotic divisions, and these cells directly develop into embryos. (alchetron.com)

They form characteristic cell clusters in suspension culture that express a set of genes associated with pluripotency and can differentiate into endodermal, ectodermal and mesodermal cells both in vitro and in vivo. (wikipedia.org)
It wasn't until more than 40 years after Gurdon's work that Shinya Yamanaka and his colleagues in Japan identified the key genes that control this "reprogramming" of adult cells. (regenhealthsolutions.info)
Yamanaka and his team identified just four genes that, if expressed in adult skin cells, could convert mature cells back into pluripotent stem cells that could become any cell in the body. (regenhealthsolutions.info)
The very important question to be addressed at that time was whether all cell types in the body have the same set of genes. (biologists.com)
So the population of molecules inside the cell can vary extensively even if the genes do not. (blogspot.com)
Since, as described above, the composition of the cell's interior and the activity of many of its proteins depend on more than just the genes, the portion of the genes' information content that is actually used by the cell is determined, in part, by non-genetic factors. (blogspot.com)

They are classified as either totipotent (iTC), pluripotent (iPSC) or progenitor (multipotent - iMSC, also called an induced multipotent progenitor cell - iMPC) or unipotent - (iUSC) according to their developmental potential and degree of dedifferentiation. (wikipedia.org)

One example is the transformation of iris cells to lens cells in the process of maturation and transformation of retinal pigment epithelium cells into the neural retina during regeneration in adult newt eyes. (wikipedia.org)

In Drosophila imaginal discs, cells have to choose from a limited number of standard discrete differentiation states. (wikipedia.org)

The implications of the Gurdon/Yamanaka discovery have been wide-ranging and continue to help scientists understand cell biology and development. (regenhealthsolutions.info)

Transgenic frogs that express the enzyme in the germline can be bred with animals harboring a transposon substrate to generate double transgenic lines where remobilization will occur in the germline in subsequent generations. (biomedcentral.com)
DNA-ligase activity in eukaryotic cells is carried out by two different molecular forms of the enzyme. (silverchair.com)
In fact, the normal level of activity for the heavy molecular form of the enzyme has been established by the time the egg enters cleavage, 7h after activation. (silverchair.com)
In the same cytoplasmic environment, and following egg activation and DNA replication, the gene for DNA-ligase I introduced by the male pronucleus is unable to direct any production of the corresponding enzyme. (silverchair.com)

Other mid-gastrula organizer cells join the expanding mesodermal layer and colonize the cranial and heart mesoderm. (silverchair.com)

Gurdon's work provided a fundamental paradigm shift for developmental biologists: an adult cell, in an already differentiated state, was not permanently stuck in that state as had been previously thought. (regenhealthsolutions.info)
Genetic manipulation of this tractable model system would further enhance the use of the frog in developmental studies. (biomedcentral.com)
Transposon vectors can be used in the frog for transgenesis and for insertional mutagenesis where enhancer trap and gene trap constructs are used to identify genomic loci involved in developmental processes. (biomedcentral.com)
Several features of amphibian embryonic life make these animals useful as models for studying early developmental events. (biomedcentral.com)
Depending on the developmental stage and the tissue considered, types of cell are available that express exclusively either one or the other of the two DNA-ligases with a defined level of activity. (silverchair.com)

In 1924 Hans Spemann and Hilde Mangold demonstrated the key importance of cell-cell inductions during animal development. (wikipedia.org)
1) The experimenter dissects a donor larva, which is in the third instar stage of development, and removes the optic disc (colored red) with a micropipette. (asu.edu)
Once perceived as an unimportant occurrence in living organisms, cell degeneration was reconfigured as an important biological phenomenon in development, aging, health, and diseases in the twentieth century. (asu.edu)

Yamanaka was able to induce adult mouse cells to a pluripotent state whereby the cells mimicked embryonic stem cells and could become any cell type in the body. (regenhealthsolutions.info)

iPS cells have shown promise as a tool in predicting how particular patients will respond to potential therapies. (regenhealthsolutions.info)
For example, experimental iPS cell therapies are being investigated that may one day replace neurons in Parkinson's Disease patient brains, different cell types of the eye for degenerative eye conditions , heart cells for heart disease , and more. (regenhealthsolutions.info)

After injury, mature terminally differentiated kidney cells dedifferentiate into more primordial versions of themselves and then differentiate into the cell types needing replacement in the damaged tissue Macrophages can self-renew by local proliferation of mature differentiated cells. (wikipedia.org)
Together, they received the award for "the discovery that mature cells can be reprogrammed to become pluripotent. (regenhealthsolutions.info)

In sexual reproduction, clones are created when a fertilized egg splits to produce identical (monozygous) twins with identical genomes. (who.int)

Since HIV-1 spreads via both free virions and cell-cell fusion, we examined the effect of the antibodies on HIV-1 Env-mediated cell-cell fusion. (preprints.org)

A variety of nontumorigenic stem cells display the ability to generate multiple cell types. (wikipedia.org)
The high fecundity of the frog can be exploited in these remobilization strategies because each outcross of X. tropicalis can generate more than 2,000 offspring. (biomedcentral.com)

The term applies not only to entire organisms but also to copies of molecules (such as DNA) and cells. (who.int)
The protein and RNA molecules produced by cells associate with each other in a context-dependent fashion or, in many cases, catalyze chemical reactions (generating lipids, polysaccharides and other molecules), whose rates depend on the temperature and composition of the external environment. (blogspot.com)

This process allows the body to replace cells not suitable to new conditions with more suitable new cells. (wikipedia.org)
The process of moving a scientific discovery into an actual treatment available for patients takes many years, even decades, and there is currently no medical treatment that directly involves iPS cells, though many are being developed and some are in clinical trial. (regenhealthsolutions.info)
In flowering plants, cells of the gametophyte can undergo this process. (alchetron.com)
In the mid-gastrula organizer, early gastrula organizer derived cells that are fated for the prechordal mesoderm are joined by the progenitors of the head process that are recruited from the epiblast previously anterior to the early gastrula organizer. (silverchair.com)

An important achievement in stem cell research was recognized in 2012, when the Nobel Prize in Physiology or Medicine was awarded to two scientists who transformed the field: Shinya Yamanaka and John Gurdon. (regenhealthsolutions.info)

Moreover, they can make this transition even in the absence of noticeable injuries and are capable of replenishing entire gastric units, in essence serving as quiescent "reserve" stem cells. (wikipedia.org)
This capacity to regenerate does not decline with age and may be linked to their ability to make new stem cells from muscle cells on demand. (wikipedia.org)
The Honeycomb Game is a word-building game: make words by clicking on cells in the honeycomb below. (claylane.uk)

In newts, muscle tissue is regenerated from specialized muscle cells that dedifferentiate and forget the type of cell they had been. (wikipedia.org)
The profile of genetic activity and the tissue contribution by cells in the organizer change during gastrulation, suggesting that the organizer may be populated by a succession of cell populations with different fates. (silverchair.com)

These cells can be analyzed in labs to uncover the underlying mechanisms of the disease, including the identification of new genetic and environmental causes. (regenhealthsolutions.info)

Outside of the body, patient-generated iPS cells retain the same genetic and/or cellular defects they do in the patient. (regenhealthsolutions.info)

For example, "chief" cells express the stem cell marker Troy. (wikipedia.org)
Clone69TRevEnv cells that express Env in the absence of tetracycline were labeled with Calcein-AM Green, and incubated with CD4+ SupT1 cells labeled with CellTrace™ Calcein Red-Orange, with or without antibodies. (preprints.org)

Collectively, the research by Gurdon and Yamanaka ushered in a new era that changed the face of stem cell research. (regenhealthsolutions.info)

With that new understanding, researchers began working to answer key biological questions that surfaced from those early experiments: what genetic, biological, or chemical components were responsible for encouraging cells to go back to an earlier state and regain the potential to become any cell type? (regenhealthsolutions.info)

By developing iPS cells from patients or patient groups, researchers can test those cells with potential drugs to develop customized treatments to optimize individual patient outcomes. (regenhealthsolutions.info)

These "diseases in a dish" can also be used screen thousands of chemical compounds to discover new drugs that could potentially treat disease-affected cells. (regenhealthsolutions.info)
and human spermatogenic stem cell culture to treat azoospermia, and to preserve fertility in pre-pubertal boys undergoing cancer treatment. (infertile.com)

PG9, PG16, PGT121, and PGT145 antibodies were identified from culture media of activated memory B-cells of an infected donor and shown to neutralize many HIV-1 strains. (preprints.org)

The reversible transformation of cells of one differentiated cell type to another is called metaplasia. (wikipedia.org)

Soon, Yamanaka and another scientist, James Thomson in the U.S., published studies showing that human cells could be similarly reprogrammed back to a pluripotent state. (regenhealthsolutions.info)

What minimal factors would be sufficient to readily reprogram cells? (regenhealthsolutions.info)

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